using System; /// <summary>装箱类。</summary> public sealed class Class<T> : IComparable, IComparable<T>, IComparable<Class<T>> { private bool _hashcode = false; private bool _equals = false; /// <summary>装箱对象。</summary> public T Value { get; set; } /// <summary></summary> public bool IsNull { get { return Value == null; } } /// <summary></summary> public bool HasValue { get { return Value != null; } } /// <summary>创建默认值。</summary> public Class(T value = default, bool tryEquals = true, bool tryHashCode = true) { Value = value; _hashcode = tryHashCode; _equals = tryEquals; } #region Override /// <summary></summary> public override int GetHashCode() { if (_hashcode && Value != null) { return Value.GetHashCode(); } return base.GetHashCode(); } /// <summary></summary> public override bool Equals(object obj) { if (_equals) { var right = obj as Class<T>; if (right == null) return false; if (Value == null && right.Value == null) return true; if (Value == null && right.Value != null) return false; if (Value != null && right.Value == null) return false; return Value.Equals(right.Value); } return base.Equals(obj); } /// <summary></summary> public override string ToString() { if (Value == null) return ""; return Value.ToString(); } #endregion #region IComparable /// <summary></summary> /// <exception cref="MissingMemberException"></exception> /// <exception cref="NotSupportedException"></exception> public int CompareTo(object obj) { if (obj != null && obj is T) return CompareTo((T)obj); if (obj != null && obj is Class<T>) return CompareTo(obj as Class<T>); if (Value == null) throw new MissingMemberException(typeof(T).FullName, nameof(Value)); if (!(Value is IComparable)) throw new NotSupportedException(); return ((IComparable)Value).CompareTo(obj); } /// <summary></summary> /// <exception cref="MissingMemberException"></exception> /// <exception cref="NotSupportedException"></exception> public int CompareTo(T other) { if (Value == null) throw new MissingMemberException(typeof(T).FullName, nameof(Value)); if (!(Value is IComparable)) throw new NotSupportedException(); return ((IComparable<T>)Value).CompareTo(other); } /// <summary></summary> /// <exception cref="MissingMemberException"></exception> /// <exception cref="NotSupportedException"></exception> public int CompareTo(Class<T> other) { if (Value == null) throw new MissingMemberException(typeof(T).FullName, nameof(Value)); if (other == null || !other.HasValue) return 1; if (Value is IComparable) return ((IComparable)Value).CompareTo(other.Value); if (Value is IComparable<T>) return ((IComparable<T>)Value).CompareTo(other.Value); throw new NotSupportedException(); } #endregion #region 运算符。 /// <summary>从 Class<T> 到 Boolean 的隐式转换,判断 Class<T> 包含值。</summary> /// <remarks>当 T 是 Boolean 时,获取 Value。<br />当 T 是 String 时,判断 Value 不为 NULL 且不为空。</remarks> public static implicit operator bool(Class<T> instance) { if (instance == null) return false; var boolean = instance as Class<bool>; if (boolean != null) return boolean.Value; var text = instance as Class<string>; if (text != null) return !string.IsNullOrEmpty(text.Value); return instance.HasValue; } // /// <summary>从 Class<T> 到 T 的隐式转换。</summary> // public static implicit operator T(Class<T> instance) => instance == null ? default : instance.Value; // /// <summary>从 T 到 Class<T> 的隐式转换。</summary> // public static implicit operator Class<T>(T value) => new Class<T>(value); #endregion }